In general, a construction machine, such as a hydraulic excavator or a wheel type hydraulic excavator, has a vehicle body that is configured of an automotive lower traveling structure, and an upper revolving structure that is mounted on the lower traveling structure to be capable of revolving thereon. A working mechanism that performs an excavating operation or the like is tiltably provided in a front portion side of the upper revolving structure. The construction machine, after self-traveling to a working site, uses the working mechanism to perform an excavating operation of earth and sand or the like.
Here, the construction machine is provided with a hydraulic motor for traveling that drives a crawler or wheels, a hydraulic motor for revolving that revolves the upper revolving structure, and various kinds of hydraulic actuators such as hydraulic cylinders that drive a boom, an arm and a bucket that form part of the working mechanism and the like. Further, the construction machine is provided with a hydraulic pump that delivers pressurized oil toward the respective hydraulic actuators, and an operation device that is operated by an operator for driving the respective hydraulic actuators.
On the other hand, the construction machine is provided with a first control valve (control valve) that is configured of a collector of a plurality of directional control valves for controlling a direction of the pressurized oil to be supplied to respective hydraulic actuators from the hydraulic pump. Aside from the first control valve, a second control valve (shuttle block) and a third control valve (solenoid valve) are provided for controlling hydraulic equipment including the hydraulic actuator and the hydraulic pump or for outputting an operation signal that is output to the directional control valve of the first control valve from the operation device (for example, Patent Document 1).